Warning or prosecuting people for failing to complete census forms was a last resort, Mr Bascand said.
"Census information is used in ways that affect everyone, from the location of schools, decisions on public transport and roads, to the rebuild of Christchurch. It's important that everyone who was in New Zealand on census night fills in a census form so that the best information possible is available.
"Statistics NZ will not share any personal information with any government department, individual or private organisation."
Completed census forms can be posted back to 2013 Census, Private Bag 208 040, Highbrook, Auckland.